This project is evaluating the associations between individual differences in platelet monoamine oxidase activity and human behavior. Biochemical studies of different human, monkey and rodent tissues have added further information that MAO types A and B are separate enzymes. Studies of psychiatric patients using more refined means to characterize individuals have focussed attention on certain features of chronic schizophrenic patients as most closely correlated with decreased MAO activity. Similarly, studies in college student populations have found moderately strong tendencies for certain personality features and psychosocial difficulties to be associated with reduced MAO activity. BIBLIOGRAPHIC REFERENCES: Murphy, D.L., Brand, E., Goldmen, R., Baker, M., Wright, C., van Kammen, D. and Gordon, E.: Platelet and plasma amine oxidase inhibition and urinary amine excretion changes during phenelzine treatment. J. Nerv. Ment. Dis. 164: 129-134, 1977. Murphy, D.L., Belmaker, R., Carpenter, W.T. and Wyatt, R.J.: Monoamine oxidase in chronic schizophrenia: Studies of hormonal and other factors affecting enzyme activity. Br. J. Psychiatry 130: 151-158, 1977.